1. Technical Field
Several aspects of the present invention relate to surface-emitting type semiconductor lasers.
2. Related Art
With applications of surface-emitting type semiconductor lasers having expanded in recent years, it is desired further to reduce the number of oscillation modes of surface-emitting type semiconductor lasers while achieving a higher output. For example, in the case of a surface-emitting type semiconductor laser having an oxide aperture, the number of oscillation modes may be reduced by reducing the diameter of the oxide aperture.
It is noted that the output of a semiconductor laser increases with an increase in the injection current, and reaches a maximum value (i.e., a rolloff point) at a certain current. This is because, in a semiconductor laser, its gain spectrum shifts with an increase in the device temperature which is caused by injection current, and the gain reaches a maximum value at a certain temperature. When the diameter of the oxide aperture of the surface-emitting type semiconductor laser is relatively small, the temperature of the device would readily elevate, and its rolloff point is reached at a relatively low injection current, such that a sufficient output may not be obtained. In this connection, in an attempt, to prevent an increase in the device temperature, Japanese laid-open patent application JP-A-2003-86895 describes a method in which a mesa reaching the current confinement region is formed around the light emitting section, and an electrode is directly formed over the groove. As a result, the distance between a heat generating section and the electrode is shortened, thereby improving the heat radiation efficiency.